Aerosol-cloud-radiation interaction during Saharan dust episodes: The dusty cirrus puzzle

Seifert, Axel; Bachmann, Vanessa; Filipitsch, Florian; Förstner, Jochen; Grams, Christian M.; Hoshyaripour, Gholam Ali; Quinting, Julian; Rohde, Anika; Vogel, H.; Wagner, Annette; Vogel, Bernhard

doi:10.5194/acp-2022-746

Cited by 4 publications

(9 citation statements)

References 51 publications

(50 reference statements)

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“…During mid‐March 2022 high loads of Saharan dust were transported to Central Europe via the Iberian Peninsula (cf. A. Seifert et al., 2023). This second case study concerns 12:00 UTC on 15 March 2022 (Figure 8).…”

Section: Resultsmentioning

confidence: 99%

“Seeing” Beneath the Clouds—Machine‐Learning‐Based Reconstruction of North African Dust Plumes

Kanngießer,

Fiedler

2024

AGU Advances

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Mineral dust is one of the most abundant atmospheric aerosol species and has various far‐reaching effects on the climate system and adverse impacts on air quality. Satellite observations can provide spatio‐temporal information on dust emission and transport pathways. However, satellite observations of dust plumes are frequently obscured by clouds. We use a method based on established, machine‐learning‐based image in‐painting techniques to restore the spatial extent of dust plumes for the first time. We train an artificial neural net (ANN) on modern reanalysis data paired with satellite‐derived cloud masks. The trained ANN is applied to cloud‐masked, gray‐scaled images, which were derived from false color images indicating elevated dust plumes in bright magenta. The images were obtained from the Spinning Enhanced Visible and Infrared Imager instrument onboard the Meteosat Second Generation satellite. We find up to 15% of summertime observations in West Africa and 10% of summertime observations in Nubia by satellite images miss dust plumes due to cloud cover. We use the new dust‐plume data to demonstrate a novel approach for validating spatial patterns of the operational forecasts provided by the World Meteorological Organization Dust Regional Center in Barcelona. The comparison elucidates often similar dust plume patterns in the forecasts and the satellite‐based reconstruction, but once trained, the reconstruction is computationally inexpensive. Our proposed reconstruction provides a new opportunity for validating dust aerosol transport in numerical weather models and Earth system models. It can be adapted to other aerosol species and trace gases.

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Section: Resultsmentioning

confidence: 99%

“Seeing” Beneath the Clouds—Machine‐Learning‐Based Reconstruction of North African Dust Plumes

Kanngießer,

Fiedler

2024

AGU Advances

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“…Despite pre-operational models simulating direct effects of mineral dust, which improves the forecast during clear-sky conditions with elevated concentrations of dust, indirect effects must be considered in order to account for dust serving as INP and altering cirrus cloud formation. A first promising attempt in this direction has recently been proposed by Seifert et al (2023), who show improved dusty cirrus representation, including the case studied here, with a novel subgrid parametrisation. The inclusion of the indirect aerosol effect is a topic of ongoing development in the ICON-ART model system and can contribute to an improved forecast of cloudiness and, closely connected, surface radiation.…”

Section: Discussionmentioning

confidence: 99%

“…However, also in ICON-ART the cirrus cloud shield in the area of elevated DOD is absent (not shown). Recalling that our ICON-ART version does not include aerosol-cloud interaction, we take this as a strong indication that dust played an important role for the formation of the high-level cloud and suggest it being a dusty cirrus cloud (Seifert et al, 2023).…”

Section: 12mentioning

confidence: 99%

“…As the model errors in cloudiness align spatially with dust above 5000 m, and comparison with station data shows improvements with the inclusion of direct effects, we conclude that dust effects are likely the source that causes these errors. Recently, Seifert et al (2023) suggested a novel subgrid parametrisation for dusty cirrus clouds and showed that only with this parametrisation is ICON-ART able to simulate the formation of these clouds. We conclude that, in particular, the missing implementation of indirect aerosol effects is likely the cause of the models not reproducing the high-level cloud in regions of high dust concentrations.…”

Section: 14mentioning

confidence: 99%

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Impact of Saharan dust outbreaks on short‐range weather forecast errors in Europe

Hermes,

Quinting,

Grams

et al. 2024

Quart J Royal Meteoro Soc

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Mineral dust, the most abundant atmospheric aerosol by mass, interacts with radiation directly and alters cloud properties indirectly. Many operational numerical weather prediction models account for aerosol direct effects by using climatological mean concentrations and neglect indirect effects. This simplification may lead to shortcomings in model forecasts during outbreaks of Saharan dust towards Europe, when climatological mean dust concentrations deviate strongly from actual concentrations. This study investigates errors in model analyses and short‐range forecasts during such events. We investigate a pronounced dust event in March 2021 using the pre‐operational ICOsahedral Nonhydrostatic weather and climate model with Aerosols and Reactive Trace gases (ICON‐ART) with prognostic calculation of dust and the operational European Centre for Medium‐Range Weather Forecasts (ECMWF) Integrated Forecasting System (IFS) model, which deploys a dust climatology. We compare model analysis and forecast with measurements from satellite and in situ instruments. We find that inclusion of prognostic aerosol and direct radiative effects from dust improves forecasts of surface radiation during clear‐sky conditions. However, dust‐induced cirrus clouds are strongly underestimated, highlighting the importance of representing indirect effects adequately. These findings are corroborated by systematic quantification of forecast errors against satellite measurements. For this we construct an event catalogue with 49 dust days over Central Europe between January 2018 and March 2022. We classify model cells by simulated and observed cloudiness and simulated dustiness in the total atmospheric column. We find significant overestimations of brightness temperature for cases with dust compared with cases without dust. For surface shortwave radiation, we find median overestimations of 6.2% during cloudy conditions with dust optical depth greater than 0.1, however these are not significant compared with cloudy conditions without dust. Our findings show that the pre‐operational ICON‐ART and the operational IFS model still do not reproduce cloudiness adequately during events with Saharan dust over Central Europe. Missing implementations of prognostic dust, particularly of indirect effects on cloud formation, lead to significant underestimations of cloudiness and potentially overestimations of surface radiation.

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“…We still don't fully understand the microphysics of these clouds, which is crucial for creating climate prediction models. (Seifert et al, 2022) postulated that the dusty cirrus forms through a mixing instability of moist clean air with drier dusty air and contends that the accurate simulation of dusty cirrus formation obviates the linear dependency on mineral dust aerosol optical depth from the bias of the radiative fluxes.…”

Section: Cirrus Cloudsmentioning

confidence: 99%

The Saharan dust plume: Current knowledge on the impact on health, human activities, and the ecosystem, with comments on research gaps

Olarewaju

Fajinmi

Davies

et al. 2023

Preprint

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A massive amount of dust estimated at a million tons is released from the Sahara Desert each year into the atmosphere and travels over the North Atlantic Ocean, commonly referred to as the Saharan dust plume (SDP). With its ability to travel over very long distances across the sea, the SDP is of enormous global importance, affecting climatic processes, and playing a significant role in nutrient cycles, sedimentary cycles, and soil development. On the other hand, from an environmental health perspective, the SDP degrades air quality, posing serious health threats to humans, especially to people with lung conditions. Recent literature documents health issues, including respiratory and cardiovascular diseases and even death in extreme cases. Despite this knowledge, large uncertainties exist in our ability to predict future trends in Saharan dust emissions and model-projected atmospheric circulation patterns. Employing a comprehensive search of the recent literature, this study reviews present knowledge of the sources, composition and propagation dynamics of the SDP and the impact of its contained atmospheric particulates on health, ecosystems, and human activities to be able to formulate credible mitigation measures and unveil areas where further research is needed for improving on these formulations. A comprehensive list of the more recent references (mainly post-dating 2010) is assembled to aid the search process of those wanting to contribute to filling these important knowledge gaps.

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Aerosol-cloud-radiation interaction during Saharan dust episodes: The dusty cirrus puzzle

Cited by 4 publications

References 51 publications

“Seeing” Beneath the Clouds—Machine‐Learning‐Based Reconstruction of North African Dust Plumes

“Seeing” Beneath the Clouds—Machine‐Learning‐Based Reconstruction of North African Dust Plumes

Impact of Saharan dust outbreaks on short‐range weather forecast errors in Europe

The Saharan dust plume: Current knowledge on the impact on health, human activities, and the ecosystem, with comments on research gaps

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